Self-regulation skills develop during childhood and are crucial for successful regulation of cognitive, affective, and social behavior throughout the lifespan. The proposed study will examine the performance of children between 4 and 8 years of age during a set of tasks aimed specifically at exploring the self-regulation component of behavior monitoring. Research indicates that performance differences between younger and older children on self-regulation tasks may be due to 1) age related changes related primarily to cognition, or 2) enhanced utilization of performance strategy. Differentiation between these two hypotheses will be examined by linking behavioral assessment of task performance to physiological measurements of active cognitive processes underlying a child's self-monitoring of behavior. Additional factors, including the role of feedback and individual differences in emotionality, will also be examined to ascertain how these variables influence the expression of self-monitoring across early childhood. We hypothesize that children's self monitoring skills will increase both as a function of age and as a result of temperamental correlates. Specifically, we predict that children who exhibit stronger physiological responses to inaccurate behavioral performance, regardless of age, will also demonstrate temperamental characteristics associated with low inhibitory control (impulsivity) and higher negative affect.